An assessment of the usefulness of winter wheat for nesting dabbling ducks in North and South Dakota
Skone, Brandi Renee.
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The Prairie Pothole Region (PPR) of North America is highly valuable for breeding waterfowl, however over the last century has been predominantly converted to some form of agriculture. With the recent increase in economic value of some cash-crops and the potential to lose highly valuable nesting habitat in the Conservation Reserve Program (CRP), there has been interest in evaluating alternative farming practices to provide additional breeding habitat for waterfowl. We evaluated and compared daily survival rates (DSR) of nests in winter wheat to nests in perennial cover and examined the number of hatched nests per hectare in each habitat to put habitat-specific estimates of nest survival in perspective. We studied nest survival of duck nests (Anas spp.) in winter wheat (n=1,170) and perennial cover (n=3,041) in the PPR of North and South Dakota on 13 to 19, 10.36-km 2 sites each year between 2010 and 2012. . We used an information-theoretic approach to develop and evaluate a set of competing models based on covariates of interest and what has been established important in the waterfowl nest-survival literature. Our top model included a set of covariates that were either highly or moderately supported in all of the models that received substantial amounts of support from the data. Across all species, we found evidence that nest survival was at least as high in winter wheat as in perennial cover, and for several species, estimated nest-survival rates were higher in winter wheat. Nest survival also varied by year and study area, was positively related to nest age and vegetation density, and was negatively related to the number of wetland basins and the proportion of cropland in the landscape. Our estimates for hatched nests per hectare were twice as high in perennial cover compared to values for winter wheat fields. However, estimates for fields of winter wheat were 6.5 times higher than estimates in spring wheat fields. Our results provided evidence that winter wheat could be a useful tool for wildlife managers seeking to add nesting habitat in landscapes used for modern agriculture.